U.S. lawmakers have expressed skepticism about North Korea's commitment during the last round of six-party talks to abandon its nuclear programs. In testimony Thursday to the House International Relations Committee the chief U.S. negotiator in the talks, Assistant Secretary of State for East Asian Affairs Christopher Hill, tried to reassure members of Congress, but predicted more tough negotiations ahead.

Mr. Hill says that in the negotiations, the United States conveyed to North Korea the absolute importance of verifiable and irreversible compliance and denuclearization.

Pyongyang, he says, should be clear at this stage what the United States, and its partners in the talks expect.

"First, we want them to abandon their weapons and by abandon we mean to have them essentially taken away. We need for them to abandon all nuclear programs, all existing nuclear programs," he said.

Mr. Hill says these steps must be verified through credible international means. North Korea, he adds, will be expected to come into full compliance with the nuclear nonproliferation treaty, and stop proliferating nuclear technology.

The September 19 deal has been thrown into doubt by North Korea's insistence, repeated on Thursday, that it receive a light water nuclear reactor before it returns to the nonproliferation treaty or allows inspections.

On this point, Mr. Hill makes clear the Beijing accord provides only for eventual discussion of the subject of a reactor.

"If [North Korea] takes that to mean that they must get a light water reactor before they abandon their weapons programs, that is a willful mis-reading of the agreement, and it means essentially that they are backing away from this agreement, backing away from us, and backing away from all our other partners," Mr. Hill added.

Language in the Beijing accord concerning a light water reactor reminds many lawmakers of the Agreed Framework during the Clinton administration, which collapsed amid North Korean violations involving uranium enrichment.

Congressman Henry Hyde expresses concern that uranium enrichment is not mentioned in the Beijing accord, and says verification will be key to any final agreement.

"Such a final deal must be air-tight to ensure we have not given away the farm with little in return beyond more broken promises from Pyongyang," noted Mr. Hyde.

Congressman Tom Lantos, who has twice held talks with North Korean officials in Pyongyang, calls the Beijing agreement a major step toward peace on the Korean peninsula, but adds the six-party talks are still, in his words, a long shot at best.

Mr. Lantos raised another issue he says Pyongyang must understand as the talks continue.

"It remains truly disturbing that there has been no improvement whatsoever in the human rights situation in North Korea," he added.

In his testimony Thursday, Assistant Secretary Hill said North Korea should understand the importance of the U.S. assurance, repeated in the talks, that the United States has no intention of attacking North Korea.

The next phase of the six-party negotiations is scheduled for next month in Beijing, talks Mr. Hill says will begin to work out the timing of North Korea's denuclearization, and measures others will take as the process hopefully moves ahead.